ice: fix potential NULL pointer deref in error path of ice_set_ringparam()

ice: fix potential NULL pointer deref in error path of ice_set_ringparam()

ice_set_ringparam nullifies tstamp_ring of temporary tx_rings, without
clearing ICE_TX_RING_FLAGS_TXTIME bit.
When ICE_TX_RING_FLAGS_TXTIME is set and the subsequent
ice_setup_tx_ring() call fails, a NULL pointer dereference could happen
in the unwinding sequence:

ice_clean_tx_ring()
-> ice_is_txtime_cfg() == true (ICE_TX_RING_FLAGS_TXTIME is set)
-> ice_free_tx_tstamp_ring()
  -> ice_free_tstamp_ring()
    -> tstamp_ring->desc (NULL deref)

Clear ICE_TX_RING_FLAGS_TXTIME bit to avoid the potential issue.

Note that this potential issue is found by manual code review.
Compile test only since unfortunately I don't have E830 devices.

Fixes: ccde82e90946 ("ice: add E830 Earliest TxTime First Offload support")
Signed-off-by: Kohei Enju <kohei@enjuk.jp>
Reviewed-by: Paul Greenwalt <paul.greenwalt@intel.com>
Tested-by: Rinitha S <sx.rinitha@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20260416-iwl-net-submission-2026-04-14-v2-8-686c33c9828d@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>